Small Intestine & Pancreas Lecture Notes

Vocabulary flashcards covering anatomy, physiology, and biochemical processes of the small intestine and pancreas as discussed in the lecture.

Small intestine

Long, coiled digestive tube that completes chemical digestion of chyme and absorbs nutrients; composed of duodenum, jejunum, and ileum.

Duodenum

First 10-inch section of the small intestine; receives acidic chyme and begins neutralization and digestion.

Jejunum

Middle (~3-ft) portion of the small intestine where most digestion and nutrient absorption occur.

Ileum

Final ~6-ft segment of the small intestine; contains Peyer’s patches and continues absorption.

Chyme

Liquefied mixture of partially digested food and gastric secretions delivered from the stomach to the small intestine.

Plicae circulares

Macroscopic circular ridges lining the small-intestinal wall that increase surface area for absorption.

Villus

Microscopic finger-like mucosal projection covering plicae circulares that further enlarges absorptive surface area.

Microvilli

Tiny membrane extensions on apical surface of enterocytes forming the brush border and housing digestive enzymes.

Peyer’s patches

Large lymphatic nodules in the ileum that provide immune surveillance against gut pathogens.

Mesentery

Double layer of peritoneum that suspends intestines, stores fat, and carries vessels & nerves.

Greater omentum

Large apron-like mesentery that drapes over the small and large intestines.

Peritoneum

Serous membrane lining the abdominal cavity (parietal layer) and covering organs (visceral layer).

Parietal peritoneum

Outer surface of the peritoneum lining the body wall.

Visceral peritoneum

Inner layer of peritoneum that directly covers abdominal organs.

Lacteal

Wide lymphatic capillary within a villus that absorbs chylomicrons (dietary fats).

Intestinal crypt (crypt of Lieberkühn)

Tubular intestinal gland between villi that secretes bicarbonate-rich watery fluid.

Goblet cell

Mucous-secreting epithelial cell scattered among enterocytes for lubrication & protection.

Enterocyte

Simple columnar absorptive cell lining the small-intestinal mucosa.

Active transport

Energy-requiring movement of molecules across a membrane against their gradient via pumps.

Facilitated diffusion

Carrier-mediated passive transport of substances down a gradient.

Osmosis

Passive movement of water across a semipermeable membrane toward higher solute concentration.

Aquaporin

Membrane channel protein that permits rapid water movement through cell membranes.

Peristalsis

Rhythmic waves of muscular contraction that propel intestinal contents forward.

Segmentation

Back-and-forth intestinal contractions that mix chyme with digestive secretions.

Bile salts

Amphipathic molecules in bile that emulsify large fat droplets into smaller micelles.

Emulsification

Process by which bile salts break large lipid droplets into tiny ones, increasing surface area for lipase.

Micelle

Tiny droplet of fatty acids & monoglycerides coated by bile salts within the intestinal lumen.

Triglyceride

Neutral fat molecule rebuilt inside enterocytes from absorbed fatty acids & monoglycerides.

Chylomicron

Protein-coated triglyceride droplet exocytosed from enterocytes and absorbed into lacteals.

Lipase

Fat-digesting enzyme that splits triglycerides into fatty acids and monoglycerides.

Peptidase (Protease)

Enzyme family that hydrolyzes peptide bonds in proteins into smaller peptides or amino acids.

Sucrase

Brush-border enzyme that converts sucrose into glucose and fructose.

Maltase

Brush-border enzyme that splits maltose into two glucose molecules.

Lactase

Enzyme that breaks lactose into glucose and galactose; deficiency leads to lactose intolerance.

Pancreatic juice

Alkaline fluid containing bicarbonate and numerous digestive enzymes secreted into the duodenum.

Pancreatic acinus

Cluster of exocrine cells in the pancreas that produces pancreatic juice.

Islets of Langerhans

Endocrine cell clusters in the pancreas that secrete hormones such as insulin and glucagon.

Hepatopancreatic sphincter (of Oddi)

Smooth-muscle valve controlling entry of bile and pancreatic juice into the duodenum.

Secretin

Duodenal hormone that stimulates pancreatic bicarbonate secretion and bile production.

Cholecystokinin (CCK)

Duodenal hormone that stimulates pancreatic enzyme secretion and gallbladder contraction.

Major duodenal papilla

Larger mucosal projection where the main pancreatic duct and common bile duct empty into the duodenum.

Minor duodenal papilla

Smaller opening where the accessory pancreatic duct empties into the duodenum.

Vagus nerve

Parasympathetic nerve that promotes pancreatic secretion and relaxation of duodenal sphincters during digestion.

Bicarbonate ion (HCO₃⁻)

Alkaline ion that buffers gastric acid and raises duodenal pH.

Nuclease

Pancreatic enzyme that digests DNA and RNA into nucleotides.

Amylase

Carbohydrate-digesting enzyme that breaks starch into smaller sugars.

Lipophobic

Describing molecules that do not dissolve in lipids and cannot readily cross lipid membranes.

Lipophilic

Describing molecules that dissolve in lipids and can easily cross cell membranes.